Washing machines typically include a cabinet that receives a tub for containing wash and rinse water. A wash basket is rotatably mounted within the wash tub. A drive assembly and a brake assembly can be positioned with respect to the wash tub and configured to rotate and control the rotation of the wash basket within the wash tub to cleanse the wash load loaded into the wash basket. During a wash cycle, water is typically extracted from the wash load by revolving the wash basket containing the wash load at a high rotational velocity. Centrifugal forces pull the majority of the water out of the wash load and through perforations in the rotating basket. A pump assembly can be used to rinse and drain the extracted water to a draining system.
The rotating basket and wash tub are typically supported by a suspension system designed to dampen translational motion induced by any imbalance with in the rotating basket. High stresses are sometimes encountered within the basket, drive system, and suspension system during the high-speed spin action used for water extraction during normal wash cycles. An out of balance mass in the wash load during a high-speed spin cycle can generate significant forces, leading to damage to the washer. For instance, with an imbalance within the wash load, a force is generated which is proportional to the product of the mass, the distance between the imbalance and the center of rotation, and the square of the velocity. Continued spin operation with an out of balance load causes unnecessary wear and tear on mechanical and electrical components in the washer and reduces the reliability of the product over time.
Conventional imbalance detection techniques can require operating the washing machine at a predetermined rotational speed to determine an out of balance condition. For instance, such techniques can require ramping the washing machine down to the predetermined rotational speed, which can result in additional cycle time and power loss.